Many chemical processes are catalytically activated to convert less valuable feed components into more valuable products. For example, 1-hexene can be produced in high selectivity via ethylene trimerization using homogeneous, single-site chromium catalyst systems, activated by a molar excess of alkyl aluminums such as methyl alumoxane (MAO) and modified methyl alumoxane (MMAO). 1-Hexene has many potential uses, one of which is as a comonomer in higher order polyolefin reactions. The reactions to form higher order polyolefins, such as polyethylenes of varying grades, are dependent on the comonomer introduced into the reaction. As the demand for polyethylenes that incorporate one or more comonomer, the demand for 1-hexene and other select comonomers also increases. The trimerization reaction of ethylene to 1-hexene represents one method of manufacturing desired oligomer product as needed. Similarly, 1-octene and other desired oligomer products can be produced in high selectivity via ethylene oligomerization using homogeneous chromium catalyst systems activated by an appropriate aluminum compound. Such selective oligomerization reactions have been performed for many years with many optimization efforts. Exemplary past processes descriptive of the reaction chemistry can be found at least in U.S. Pat. No. 7,157,612, and in International Patent Publication Nos. WO2007/092136 and WO2009/060343, each of which is incorporated herein by reference in its entirety for all purposes. One of the major challenges associated with the selective oligomerization of ethylene (or other olefins) is the control of the reaction to maximize production rates while maintaining selectivity to the desired oligomer and maximizing catalyst utilization rates.
One part of controlling these chemical processes is the step of quenching the catalyst. Typically quenching can be achieved by introducing a component that converts the catalyst composition to a composition that can no longer promote the reaction of the feed components. Such components are sometimes referred to as “catalyst-deactivating compositions.” The amount of catalyst-deactivating composition necessary to completely deactivate the catalyst composition can be calculated from the chemical equation of the deactivation reaction. But due to a number of factors (e.g., insufficient mixing), incomplete deactivation can occur even in the presence of sufficient amounts of the catalyst-deactivating composition. Problems associated with incomplete mixing can be aggravated when the reaction product mixture includes more than one liquid phase because the catalyst and the catalyst-deactivating composition may partition at different concentrations in the two phases, thereby creating a relative depletion of catalyst-deactivating composition in the phase to which the catalyst migrates despite the presence of sufficient quantities of catalyst-deactivating composition in the overall mixture. In other processes, the catalyst composition can migrate from solution to the vapor phase as the solvent evaporates. The presence of the catalyst in the vapor phase allows for further reactions creating unwanted by-products (e.g., aluminum-containing precipitates) that may clog piping or lead to processing problems.
There is therefore a need for a method of deactivating a catalyst that avoids problems associated with incomplete mixing and downstream catalytic activity leading to processing problems. Such a method would be particularly useful in an oligomerization process since oligomerization processes often produce multiphase product streams whereby the oligomers are separated by volatilization.